Poly (ester-carbonate)s are a class of engineering plastics which are commercially produced by the industry and find application as high performance materials. The introduction of carbonate linkage in the matrix of a polyester has the beneficial effect of improving processability, reducing the glass transition temperature and improving impact strength. The ester component of the poly (ester-carbonate)s can be derived either from poly (arylester) or a poly (alkylester).